Celastrales is an
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of flowering plants. They are found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. There are about 1200 to 1350 species in about 100
generaIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
. All but 7 of these genera are in the large
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
CelastraceaeThe Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
. Until recently, the composition of the order and its division into families varied greatly from one author to another.
Celastrales is a diverse order that has no conspicuous unique characteristic and is consequently hard to recognize.
Celastrales is an
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of flowering plants. They are found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. There are about 1200 to 1350 species in about 100
generaIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
. All but 7 of these genera are in the large
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
CelastraceaeThe Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
. Until recently, the composition of the order and its division into families varied greatly from one author to another.
Description
Celastrales is a diverse order that has no conspicuous unique characteristic and is consequently hard to recognize. The flowers are usually small with a conspicuous nectary disk. The
stipuleIn botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk...
s are small or rarely absent. The micropyle has 2 openings and is therefore called a bistomal micropyle. Flowers with well-developed male and female parts are often functionally unisexual. The seed often has an
arilAn aril is any specialized outgrowth from the funiculus that covers or is attached to the seed...
. In bud, the
sepalA sepal is a part of the flower of angiosperms . Sepals in most flowers are green and lie under the more conspicuous petals. As a collective unit the sepals form a calyx, whereas the collection of petals is called the corolla...
s have a quincuncial arrangement. This means that 2 sepals are inside, 2 are outside, and the other has one side covered and one side exposed.
Relationships
Perhaps the most conspicuous and unusual trait of Celastrales is the nectary disk, a feature that it shares with another
rosidThe rosids are a large group of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms. It is divided into 16 to 20 orders, depending upon circumscription and classification. These orders, in turn, together comprise about 140 families...
order,
SapindalesSapindales is a botanical name for an order of flowering plants. Well-known members of Sapindales include citrus; maples, horse-chestnuts, lychees and rambutans; mangos and cashews; frankincense and myrrh; and mahogany....
. Since the 2 orders are not closely related, the disk must have been an independent development in each of these 2 lines.
Celastrales is a member of the COM clade of Fabidae, with Fabidae being one of the 2 groups of Eurosids. The COM clade consists of 3 orders, Celastrales,
OxalidalesThe Oxalidales are an order of flowering plants, included within the rosid subgroup of dicotyledons. The following families are typically placed here:* Family Brunelliaceae* Family Cephalotaceae * Family Connaraceae...
,
MalpighialesMalpighiales is one of the largest orders of flowering plants, containing about 16000 species, approximately 7.8% of the eudicots. The order is very diverse and hard to recognize except with molecular phylogenetic evidence. It is not part of any of the classification systems that are based only...
, and 1 unplaced family, Huaceae. Hardly anything is known about how the 4 parts of the COM clade are related to each other.
Circumscription
The name Celastraceae was first used by Thomas Baskerville in 1839. In the time since Baskerville first defined the order, until the 21st century, there were great differences of opinion about what should be included in the order and in its largest family,
CelastraceaeThe Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
. The family Celastraceae was the only group consistently placed in the order by all authors. Because of the ambiguity and complexity of its definition, Celastraceae became a dumping ground for genera of dubious affinity. Several genera were assigned to this family with considerable doubt about whether they really belonged there. Also, some genera that properly belong in Celastraceae were placed elsewhere.
By the end of the 20th century,
GoupiaGoupia is a neotropical genus of flowering plants and the sole genus included in the family Goupiaceae. There are three species, all found in tropical northern South America.Species*Goupia cinerascens...
and Forsellesia had been excluded from Celastraceae and also from Celastrales. Goupia is now in
MalpighialesMalpighiales is one of the largest orders of flowering plants, containing about 16000 species, approximately 7.8% of the eudicots. The order is very diverse and hard to recognize except with molecular phylogenetic evidence. It is not part of any of the classification systems that are based only...
. Forsellesia is now in Crossosomatales. It continues to be the subject of a dispute about whether its proper name is Forsellesia or
GlossopetalonGlossopetalon is a small genus of shrubs in the plant family Crossosomataceae. These plants are sometimes called greasebushes. They are native to the western United States and northern Mexico, where they can be found on dry mountain slopes...
.
After being placed elsewhere, Canotia, Brexia, and Plagiopteron were found to belong in Celastraceae. The family Hippocrateaceae was found to be deeply nested within Celastraceae and is no longer recognized as a separate family.
In 2000, Vincent Savolainen and co-authors found that 3 families -
LepidobotryaceaeLepidobotryaceae is a flowering plant family in the order Celastrales. It contains only two species, Lepidobotrys staudtii and Ruptiliocarpon caracolito. Lepidobotrys staudtii is a small African tree, ranging from Cameroon eastward to Ethiopia. Ruptiliocarpon caracolito is a large tree, locally...
,
ParnassiaceaeParnassiaceae is a family of Flowering plants in the Eudicot order Celastrales. The family has only two genera, Lepuropetalon and Parnassia....
, and
CelastraceaeThe Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
- were closely related and they stated that these should constitute the order Celastrales. They also excluded
LophopyxisLophopyxis is a genus of flowering plants and the sole genus of the family Lophopyxidaceae. The group consists of 2 species of tendrillate lianas. They are found in the Sunda Islands....
from Celastrales. Lophopyxis now constitutes a monogeneric family in Malpighiales.
In a DNA study in 2001, Mark Simmons and others confirmed all of these results except for the placement of Lophopyxis and Lepidobotryaceae, which they did not sample.
In 2006, Li-Bing Zhang and Mark Simmons produced a phylogeny of Celastrales based on
nuclearIn cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as...
ribosomalRibosomes are complexes of RNA and protein that are found in all cells. The ribosome is part of the mechanism that translates the DNA sequence into the protein sequence. Ribosomes from bacteria, archaea and eukaryotes , have significantly different structure and RNA...
and
chloroplastChloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.The word chloroplast is...
DNA. Their results showed that
BhesaBhesa is a genus of plant in family Celastraceae.Species include:* Bhesa ceylanica, Ding Hou* Bhesa nitidissima, Kosterm.* Bhesa paniculata, Arn.* Bhesa robusta, Ding Hou...
and
PerrottetiaPerrottetia is an unplaced genus of flowering plant in the order Huerteales. The fifteen species occur in Asia from China to Australia, and in the Americas from Mexico to Peru.Species include:* Perrottetia excelsa* Perrottetia multiflora...
were misplaced in Celastraceae. Bhesa is now in Centroplacaceae, a family in Malpighiales. and Perrottetia is in
HuertealesHuerteales is the botanical name for an order of flowering plants. It is one of about 16 to 20 orders that make up the large eudicot group known as the Rosids. Within the rosids, it is one of the four orders in Malvidae, a group known informally as the malvids or eurosids II...
. Zhang and Simmons found Pottingeria and
MortoniaMortonia is a small genus of flowering shrubs known as saddlebushes or mortonias. These are rough, hairy shrubs with leathery leaves and panicles of fleshy white to purplish flowers. They bear nutlets containing 1 seed each...
to be closely related to the families Parnassiaceae and Celastraceae, but not in either of them. These two genera are therefore in Celastrales. They found that
SiphonodonSiphonodon is a genus of plant in family Celastraceae.Species include:* Siphonodon celastrineus, Griff....
and Empleuridium are proper members of Celastraceae, removing considerable doubt about their placement there. They also showed that the small family Stackhousiaceae, consisting of three genera, is embedded in Celastraceae. Most of these results were confirmed by the second phylogeny of Celastrales, which was produced by Mark Simmons and several co-authors in 2008.
Nicobariodendron sleumeri, the only member of its genus, continues to be an enigma. It is a small tree from the
Andaman and Nicobar IslandsThe Andaman and Nicobar Islands is a Union Territory of India...
of India. Little is known of it and it has never been sampled for DNA. It is generally thought to belong in Celastrales, but this is not a certainty.
Families
Celastrales has been divided into families in various ways. In their APG II classification in 2003, the
Angiosperm Phylogeny GroupThe Angiosperm Phylogeny Group, or APG, refers to two international groups of systematic botanists who came together to try to establish a consensus view of the taxonomy of flowering plants that would reflect new knowledge in angiosperm relationships based upon molecular systematics studies...
recognized 3 families in Celastrales -
LepidobotryaceaeLepidobotryaceae is a flowering plant family in the order Celastrales. It contains only two species, Lepidobotrys staudtii and Ruptiliocarpon caracolito. Lepidobotrys staudtii is a small African tree, ranging from Cameroon eastward to Ethiopia. Ruptiliocarpon caracolito is a large tree, locally...
,
ParnassiaceaeParnassiaceae is a family of Flowering plants in the Eudicot order Celastrales. The family has only two genera, Lepuropetalon and Parnassia....
, and
CelastraceaeThe Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
. At the
Angiosperm Phylogeny WebsiteAngiosperm Phylogeny Website is a well known web site dedicated to research on Angiosperm phylogeny and taxonomy.The site is hosted by the Missouri Botanical Garden website and maintained by researcher Peter F. Stevens, who is a member of the Angiosperm Phylogeny Group...
, Peter F. Stevens has recognized these 3 families and added a 4th, Pottingeriaceae, consisting only of Pottingeria.
Lepidobotryaceae has 2 species, Lepidobotrys staudtii, and
RuptiliocarponRuptiliocarpon is a monotypic genus of flowering plants in the family Lepidobotryaceae. The genus has only one species, Ruptiliocarpon caracolito. It is a tall tree that grows in several small isolated areas of central and South America. It is known from Costa Rica, Colombia, Peru, and Suriname...
caracolito.
ParnassiaceaeParnassiaceae is a family of Flowering plants in the Eudicot order Celastrales. The family has only two genera, Lepuropetalon and Parnassia....
has 2 genera.
LepuropetalonLepuropetalon is a genus of flowering plants in the family Parnassiaceae. It is one of the two genera in the family, the other being Parnassia. Lepuropetalon has only one species, Lepuropetalon spathulatum. It is a winter annual that is most abundant in eastern Texas and western Louisiana...
is monospecific, (Lepuropetalon spathulatum) and Parnassia has about 70 species.
In the 2006 phylogeny, Nicobariodendron was not sampled, but those species that were sampled fell into 2 strongly supported clades. One was a small clade consisting only of the family Lepidobotryaceae. The other was a very large clade containing the rest of the order. They found the large clade to be divided into 5 strongly supported groups. These are the family Parnassiaceae, the genus Pottingeria, the genus
MortoniaMortonia is a small genus of flowering shrubs known as saddlebushes or mortonias. These are rough, hairy shrubs with leathery leaves and panicles of fleshy white to purplish flowers. They bear nutlets containing 1 seed each...
, a pair of genera from Celastraceae (Quetzalia and
ZinowiewiaZinowiewia is a genus of plants in the family Celastraceae.Species include:* Z. costaricensis Lundell* Z. madsenii C. Ulloa & P. Jørg.* Z. micrantha Lundell...
), and the rest of Celastraceae. No relationships were resolved among these 5 groups.
In 2008, Simmons and others produced a phylogeny of Celastrales that achieved better resolution than the 2006 study by sampling more species and more DNA. In the large clade of Celastrales, they found the same 5 groups that were found in the 2006 study. However, there was weak to moderate support for a clade of (Pottingeria + Mortonia), and weak support (56%
maximum likelihoodMaximum likelihood estimation is a popular statistical method used for fitting a statistical model to data, and providing estimates for the model's parameters....
bootstrapIn statistics, bootstrapping is a modern, computer-intensive, general purpose approach to statistical inference, falling within a broader class of resampling methods....
percentage) for a clade containing Quetzalia, Zinowiewia, and the rest of Celastrales.
The division of Celastrales into families is clearly in need of revision, but further studies will be needed to determine the best way to do so. It is not yet clear whether Pottingeria and Mortonia are best placed into monogeneric families or combined into a single family. The weak support for the inclusion of Quetzalia and Zinowiewia in Celastraceae is a bit of a surprise, since neither had previously been thought to be an anomalous member of the family. An alternative approach would be to expand Celastraceae even further, to include Mortonia, Pottingeria, and Parnassiaceae.
Phylogeny
The following phylogenetic tree was made by combining parts of three different trees. Bootstrap support is 100% except where shown. Branches with less than 50% bootstrap support are collapsed. The clade numbers are from Simmons et alii (2008).
External links
- Phylogeny 2008 Mark P. Simmons, et alii (2008). Mol.Phyl.Evol. 48(2):745-757.
doi:10.1016/j.ympev.2008.04.039